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Clinical Neuroscience

MAY 30, 2017

[EEG-based cerebral networks in 14 neurological disorders]

DÖMÖTÖR Johanna, CLEMENS Béla, CSÉPÁNY Tünde, EMRI Miklós, FOGARASI András, HOLLÓDY Katalin, PUSKÁS Szilvia, FEKETE Klára, KOVÁCS Attila, FEKETE István

[Background - Brain networks have not been systematically investigated yet in most neurological disorders. Purpose - To investigate EEG functional connectivity (EEGfC) networks in 14 neurological disorders. Patients - Potentially eligible patients were collected from clinical and EEG databases. All the available clinical data and EEG records were critically revised. All the patients who suffered of a single neurological disorder (out of the 14) and had a good quality EEG recording entered the study. Confoundig factors as comorbidity and CNS-active drug effects were eliminated as far as possible. EEG analysis - Three minutes of resting-state, waking EEG activity were selected for analysis. Current source density (CSD) values were computed for 2394 cortical voxels by Low Resolution Electromagnetic Tomography (LORETA). Thereafter, Pearson correlation coefficients were computed between all pairs of 23 cortical regions of interest (ROI) in each hemisphere (LORETA Source Correlation, LSC software). Computation was carried out for conventional EEG broad bands and very narrow bands (1 Hz bandwidth) between 1 and 25 Hz as well. Correlation coefficients of each group were statistically compared to our normative EEG (LSC) database by two-talied t-tests. Bonferroni-corrected p<0.05 values were accepted as statistically significant, and were graphically displayed as topographical networks. Results and conclusion - Group-specific networks were demonstrated. However, non-specific networks, charasteristic for most groups, were detected as well. Common finding were: decreased connectivity in the alpha band and increased connectivity in the delta, theta bands and upper-beta band. Decreased alpha-band connectivity presumably reflected primary lesional effects and on the other hand, non-specific vulnerability of “rich club connections”. Increased connectivity in the slow bands presumably indicated adaptive-compensatory activity of brain homeostasis. ]

Clinical Neuroscience

SEPTEMBER 30, 2015

Extreme delta brush EEG pattern in a case with anti-NMDA receptor encephalitis

SÖYLEMEZ Elif, GÜVELI Tekin Betül, ATAKLI Dilek, YATMAZOGLU Merve, ATAY Turan, DAYAN Cengiz

Anti-N-methyl-D-aspartate receptor NMDA-R encephalitis is caused by antibodies against the NMDA-R and characterized by a severe encephalopathy with psychosis, epileptic seizures and autonomic disturbances. This disorder is often accompanied with malignancies, especially ovarian teratoma. Some patients’ EEGs show a different pattern similar to the waveforms of premature infants and this pattern is specifically named as extreme delta brush (EDB). We report a 24-year-old female having anti-NMDA receptor encephalitis and EDB patern.

Hypertension and nephrology

JULY 20, 2013

[Practical aspects of therapy by erythropoiesis stimulating agents in renal anaemia]

DEÁK György, HERSZÉNYI Eszter, AMBRUS Csaba, KISS István

[Prevalence of renal anaemia due to insufficient production of erythropoietin increases progressively in the course of renal function deterioration. Renal anaemia is treated by erythropoesis stimulating agents (ESA). Outcomes of randomized clinical trials have taught us to avoid the strategy of normalization of hemoglobin (HGB) levels by ESA therapy as it may increase the risk of cardiovascular events and mortality. The Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline for Anaemia published in 2012 recommends to start ESA therapy in the 90-100 g/l HGB range and suggests to keep HGB concentrations below 115 g/l. It is an inappropriate strategy to aim at normalizing hemoglobin (HGB) levels by ESA therapy because it may lead to progressive escalation of ESA doses even in the presence of diminished ESA responsiveness. High ESA doses and diseases causing ESA hyporesponsiveness eg. infections, chronic inflammation, malnutrition, insufficient dose of dialysis, severe hyperparathyroidism, iron deficiency are related to increased risk of mortality. KDIGO Clinical Practice Guideline for Anaemia emphasizes the importance of assessing and treating causes of ESA hyporesponsiveness, limits ESA dose escalation and recommends gradually changing ESA doses to avoid high amplitude HGB oscillation.]

Clinical Neuroscience

SEPTEMBER 23, 2011

[The methodology and objectives of registrating high frequency oscillation in epilepsy]

CLEMENS Zsófia

[Technological advances in digital EEG allowed the recording the full frequency band of the EEG. Activity beyond the traditional 0.3-70 Hz band reflects both physiological and pathological processes. High frequency activity recorded from the epileptic brain has been related to both epileptogenicity and epileptogenesis. The article reviews research avenues, clinical applications, and the methodology of detecting and quantifying high frequency activity.]

Clinical Neuroscience

MAY 30, 2006

[CHANGES IN EEG-COMPLEXITY AFTER SUBCORTICAL ISCHEMIC BRAIN DAMAGE]

MOLNÁR Márk, CSUHAJ Roland, HORVÁTH Szabolcs, VASTAGH Ildikó, GAÁL Zsófia Anna, CZIGLER Balázs, BÁLINT Andrea, NAGY Zoltán

[Introduction - Complexity analysis of the EEG is a relatively new field in theoretical and cinical electrophysiology. The authors present results of EEG-analysis in a patient with stroke, utilizing the sensitivity of the new procedures with respect to linear and nonlinear synchronization. Participants and methods - The EEG (19 channels) was recorded in a patient with subcortical unilateral ischaemic completed stroke involving the frontoparietal white matter while leaving the cortex intact and in 12 healthy controls in eyes open and in eyes closed conditions. Results - In the patient, increased Omega-complexity was found in slow (delta, theta) and lower alpha frequencies in the side of the stroke and in high frequencies (beta2 in eyes closed, alpha2, beta1 and beta2 in eyes open conditions) in the intact side. Synchronization likelihood was higher in the ischaemic side in the beta2 (eyes closed) and both in the beta1 and beta2 (eyes open) frequencies. Increasing Omega-complexity caused by eyes opening was markedly reduced in the patient in the beta frequencies compared to that seen in the controls. The difference was more conspicuous in the side of the infarct and involved not only the beta but also the alpha frequencies as well. Opening the eyes decreased synchronization likelihood in all frequency bands in the controls and also in the patient except the alpha2, beta1 and beta2 bands in the side of the lesion. Conclusions - The increased Omega-complexity and decreased synchronization likelihood in the slow frequencies in the infarcted side is probably the result of lesioned interneuronal connections lowering the level of cooperation of neuronal systems involved in this type of activity. The increased Omega-complexity and decreased synchronization likelihood caused by eyes opening could not be observed in the beta and alpha frequencies in the side of the lesion, possibly caused by damaged thalamocortical connections.]

Clinical Neuroscience

MARCH 30, 2006

[SPECTRAL EEG-CHARACTERISTICS OF SUBCORTICAL ISCHEMIC BRAIN LESION- A CASE STUDY]

MOLNÁR Márk, CSUHAJ Roland, HORVÁTH Szabolcs, VASTAGH Ildikó, GAÁL Zsófia Anna, CZIGLER Balázs, BÁLINT Andrea, NAGY Zoltán

[Introduction - Although the EEG-changes caused by ischemic stroke are well known, data of the literature are rather ambiguous. The EEGfindings recorded in a patient with a unilateral subcortical ischemic lesion are evaluated with special emphasis related to the effect of the dynamics caused by eyes opening. Participants and methods - Data recorded from a patient (54 years old male with a completed stroke involving the frontal and parietal subcortical region in the left side) were compared to those of a control group (12 healthy age matched subjects). Absolute and relative frequency spectra, theta/beta quotients, the interaction index characterizing the effect of eyes opening and the symmetry index were calculated from the EEG recorded in eyes closed and eyes open conditions. Data of the patient were compared to those recorded in the control group on the basis of 95% confidance intervals. Results - Irrespective of the recording conditions the predominance of slow activity and the increase of theta/beta quotients were found in the absolute frequency spectra. The increase of beta1 and beta2 frequency bands following eyes opening on the side of the lesion were found to be less obvious than that seen on the intact side and that observed in the control group. With respect to the interaction index related to the side differences caused by eyes opening the change of the beta2 frequency band was found to be the most conspicuous. The symmetry index underscored the predominance of slow (delta, theta, alpha1) frequencies on the lesion side, and that of the fast (beta1, beta2) frequencies on the intact side in both recording conditions. Conclusions - Localized lesion of the white matter without cortical damage can cause the predominance of slow activity and decrease of the fast frequency bands on the side of the lesion which can be shown by the absolute frequency spectra and is revealed by the symmetry index. The lack of functional reactivity of the fast frequencies in the side of the lesion can clearly be seen in the change of relative spectra following eyes opening and on the basis of the calculation of the interaction index reflecting the dynamics of side differences.]

Clinical Neuroscience

JANUARY 30, 2011

[Ageing and arithmetic performance - electrophysiological complexity-, and graph theoretical characteristics]

MOLNÁR Márk, BOHA Roland, BENYOVSZKY Máté, GAÁL Zsófia Anna, TÓTH Brigitta

[During the course of ageing the decline of cognitive performance, including attention and working memory processes - essential for arithmetic procedures - is well known. For the investigation of the neuronal mechanisms of these processes the application of methods capable of taking into account the high complexity of the nervous system, the role of nonlinear processes and network-properties of its constituents are necessary. As for the latter the recently realized small world network characteristics representing optimal conditions for information processing may be of particular importance. In the present study the spectral, complexity-, and network characteristics of the EEG recorded during performing an arithmetic task in a group of young (n=32, mean age 22.0 yrs) and elderly (n=19, mean age: 66.7 yrs) was analyzed. Heart rate and behavioral measures (number of mistakes, reaction time) were also investigated. The alpha2 band decreased in the young, while the delta band increased in the elderly in the task condition. The increased Omega-complexity observed in the elderly is probably caused by reduced interneuronal connectivity. “Small-world” network characteristics were found in the beta and delta bands although in the elderly the topology was closer to a random pattern. In the task condition the network features of the elderly subjects shifted more towards the small world pattern than those seen in the young indicating that for the elderly the mobilized effort for task completion was higher. In spite of this, the level of performance and the heart rate change observed in the elderly was lower than that seen in the young. The application of complexity-, and graph theoretical analysis appears to be a promising tool for the investigation of diseases of the nervous system characterized by diffuse pathology as in the case of as various types of dementias.]

Clinical Neuroscience

MAY 20, 2011

[The role of sleep dynamics and delta homeostasis in cognitive functions]

HALÁSZ Péter

[The paper is aimed to introduce the neuronal network basis of dynamic sleep processes, including the micro-structure of sleep and the relationship of sleep dynamics with homeostatic regulation and plastic changes during sleep. Newer studies tend to show that beyond the wellknown long-term homeostatic and circadian regulation of NREM sleep, sleep is regulated by a stimulus and arousal dependent flexible defense system, the elements of which participate in sleep delta homeostasis. Within the EEG elements of sleep a more larger amount represents reactible type as it was thought previously.. Both the events of wake state and sensory input during sleep are shaping the sleep EEG in a function- and localisation specific way and the next day cognitive functios are determined by these changes.]